Role of S-Adenosylmethionine in Methionine Biosynthesis in Yeast

Extracts of Saccharomyces cerevisiae were used to develop a cell-free system capable of converting the beta-carbon of serine into the methyl group of methionine. No requirement for either S-adenosylmethionine or S-adenosylhomocysteine could be demonstrated for net methionine biosynthesis. Growth of the cells in B(12) did not affect the reaction. The mechanism for the methylation of homocysteine in yeast appears to be similar to the non-B(12) system in Escherichia coli.